SOME IMPORTANT DEFINITIONS
Matter :-
Anything that has mass and occupies space is called matter.
Anything that has mass and occupies space is called matter.
Solid :- Solid is defined as
that form of matter which possesses rigidity, is incompressible and hence has a
definite shape and volume.
Liquid:- Liquid is defined as that form of matter which possesses
fluidity but is almost incompressible and hence has a definite volume but no
definite shape.
Gas :- Gas is defined as that
form of matter which possesses fluidity but is highly compressible and hence
has neither definite shape nor definite volume.
Characteristics of particles :
A) Large number of
particles constitute matter.
B) Particles of matter
are very small in size.
C) Particles of matter
have spaces between them.
D) Particles of matter
are continuously in motion.
E)Particles of matter
attract each other.
Interconversion of matter:The states of matter are inter-convertible. The
state of matter can be changed by changing temperature or pressure
Humidity:-The amount of water vapour present in the air is called Humidity.
Density :-It is the mass
occupied by a solid per unit volume and is obtained by dividing the mass of a
particular solid by the volume occupied.
Density = mass / volume
Fusion:-The process in which a solid changes to liquid state by absorbing
heat at constant temperature is called fusion.
Diffusion:- The process in which particles of one substance occupy the
vacant spaces present in the particles of the other substance, is called
diffusion.
Condensation :- The process in which a gas changes into liquid state by giving
out heat at constant temperature.
Latent heat :-The
hidden heat which breaks the force of attraction between the molecules during
change of state.
Latent heat of fusion:-The amount of heat energy that is needed to convert one kg of a
solid into the liquid state at atmospheric pressure at its melting point is
termed as latent heat of fusion.
Boiling point :-The temperature at
which a liquid starts boiling at the atmospheric pressure is known as boiling
point.
Freezing point :-The temperature at
which a liquid changes to solid by giving out heat at the atmospheric pressure.
Latent heat of vaporization:-The amount of heat
energy that is needed to convert one kg of a liquid at its boiling point
temperature into its vapour state without any rise in temperature, is termed as
latent heat of vaporization.
Melting point :-The melting point of a
solid may be defined as the temperature at which a solid melts to become a
liquid at the atmospheric pressure.
Sublimation:-Sublimation is the change of a solid directly into the gaseous
state without passing through the liquid state upon heating and back to the
solid state when the temperature is lowered.
Evaporation:-The phenomenon of change of liquid to the vapour state at any
temperature below the boiling point of the liquid is termed as evaporation.
Transpiration:-The process of evaporation of water from the aerial parts of plants especially leaves is called transpiration.
Evaporation is surface
phenomenon. Particles from the surface gain enough energy to overcome the
forces of attraction present in the liquid and change into the vapour state.
Evaporation causes cooling.
The rate of
evaporation is affected by the surface area exposed to atmosphere, temperature,
humidity and wind speed.
Kelvin :- S.I. unit of temperature
is Kelvin. Formula to calculate
T (K) = T (°C) + 273
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Transpiration:-The process of evaporation of water from the aerial parts of plants especially leaves is called transpiration.
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